Modulator



Fe. l, E949. P. GLASS MODULATOR Filed Nov. 14, 1946 lrwcmlo@ Paul @laws Patented Fetal, 1949 risotto MopULA'ron Paul Glass, chicago. m.. minor to Anima Regulator Company, a corporation oi Illinois Application November 14,194.6, Serial No..709,74l (ci. 332-13) 3 Claims.

This invention relates to modulators of the v type employing an electron beam tube.

An object of the invention is to devise an arrangement ior modulating the output current of an electron beam relay in which the` beam is al- 2 A, suitable source of carrier wave represented by the generator 1 is applied to denectins means, Isuch as the pair oi plates 8, or deilecting the ternately deflected between two spaced anodes or targets by 'means of a carrier wave.

A further` object 4of the invention is to devise 'a modulator in which the modulated current is formed oi' positive and negative pulses ofthe same amplitude but oi varying duration.

A further object ci' my invention is to devise an electron beam-type modulator in which the output oi' the modulator consists ci e series oi pulses having a fixed pulse frequency but oi variable pulseduration.

The objects of my invention are attained by employing a cathode ray tube provided with two spaced anodes or targets between whichthe beam l is alternately deflected by means of a carrier wave applied to suitable beam denecting means. The modulating wave or signal is appliedto vary the mean position of the beam with respect toits normal or neutral position. The arrangement is such that a small deection of thelbeamirom its neutral position causes the output. wave to reach its maximum value quickly and remain at this yvalue throughout an oscillatory excursion.

My invention may be explained by reference to the accompanying drawing in which Figure 1 is a'schematic circuit diagram oi one i embodiment thereof;

Figure 2 is a developed view ci the two tar get for exrflaining the action oi the modulator; an

Figure 3 is a series of ifour curves which illusJ trate the operation of the invention.

Referring to Figure l, i indicates the envelope of an electron beam tube having an electron son 2 for producing a concentrated electron beam la which is normally directed along an axis passing between two spaced anodes 8 and t located in the other end oi the tube. These anuales are provided with extensions te and la extending back towards the gun 2 in substantially parallel relation, and these extensions are for the purpose oi intercepting the beam'at all angles of deection. I

Anodes s and il are connected throushsuitable resistance elements 3b and tb to the pitive tei.L1 lminal oi a suitable source o space current. These anodes are also connected to a suitable load circuit. preferably through an amplifier t. i The, gun t is connected to the negative terminal oi the space current supply.'

electron -beam alternately between the anodes 3 andi.. A second deiecting system, such as the pair of plates 8, is also arranged to deflect the beam in the same plane as the plates s. and these plates are energized from a suitable signal'source represented in the drawing by the microphone lil which' is energized from battery il, and the voice currents from the microphone are applied to the plates t alter being armpitn ned at il. It is obvious that magnetic deileetins; systems may be employed ior` the carrier and signal waves ii desired.

In Figure 2 E have shown the two anodes t and l in developed position for the purpose of illustrating the extent o deflection of the beam under diierent'conditions of applied signal.

The curves of Figure 3 illmtrate the wave form obtained'across the anodes tl and diierent conditions or applied signal.-

i Operation oi the arrangement shown in Figure l is as follows: signal wave may be a periodic wave or a varys ing potential oi either polarity, but its rate .of change will normally be quite low with reference to thetirequency of the source l. Normally, the electron beam 2a will be directed between the two anodes l andt by suitable beam concentrat ins.r and directing means not shown. With the beam in its neutral. or normal position, an equal quantity oi electrons will impinse upon the anw oder, t and d and there will be ne difference of potential applied to the output circuit. The nur mal position of the beam is shown lo in ills-f ure 2. Assume that a sine wave shown in curve a, 'Figure 3, is applied to the deflection plates d. the beam will .be deflected alternately from one anode to the other at the frequency oi the car;

rier wave. Where the positive and negative als ternations of the wave are the same, the

will be deflected to the same extent on the two anodes, and this is shown in Figure t by the deection ol the beam from the normal position. So to the position b' on the anode s :for the poste tive carrier pulse and down to the position b for the negative carrier* pulse. While the beam is impinging upon the anode t the output circuit will receive a positive pulse P as shown in curve t,

^ Figure 3, and while the .beam impinges upon anode t the output circuit will receive a nega tive pulse N. When the mean position of the 'beam is at the point So in Figure 3. the positive and negative pulses oi the output wave will have It will be understood that the the same amplitude and will be or the same dura.-

tion, aee'curve b.

Assume now that the signal source applies a potential to deection plates 9 to move the mean position of the beam from the point So up to the point Sc in Figure 2 so that thebeam' normally strikes the anode 3. The value of the signal potential applied to the deflection plates 9 .is represented by the line Sc in Figure 3. The

wave shape oi the output wave will be determined by tite points at which the value Sc of Figure 3 just cancels the value of curve ay 'of Figure 3 representing the carrier wave. As will be seen from curve c of Figure 3, the application oi the signal potential Sc in a direction` to shiit the mean position of the beam onto anode 3 causes a, lengthening of the positive pulses P and a corresponding shortening of the negative pulses N. v

When the applied signal has a greater value to deect the mean position of the beam to the point Sd as shownin Figline 2, the lduration of the positive pulses will be still further increased. i

When the deecting force ofthe signal wave is" equal. to the cleecting force of the carrierwave as shown by the line Sd in Figure 3, the positive pulses P will be of maximum duration and the negative pulses will have disappeared. Under this condition, the position of the beam oscillates about the point Sd in Figure 2 and the extreme positions of the beam are represented by It'will be obvious that of the output circuit wouldextend from theanode 3 while the other side would extend from terminal 5. If the output wave is to include. negative pulses only, one side of the output circuit will extend from the lead of anode 4 and the other side from terminal 5.

For steep wave-forms at the point o! transition from positive to negative. and vice versa, the gap between the two anodes should ybe small with Irespect to the length of the anodeor themaximum swing of the beam, and the transverse dimension of the beam in the direction oi swing should also be small with respect to the maxi- Amurn swing.

In the annexed claims the term plane of said anodes refers to the plane which includes, or

is parallel with, the longitudinal axes of, the anodes.

I claim: v

1,. In combinatioman electron tube including means for establishing an electron beam along a given axis, a pair oi anodles arranged Aon opposite sides of said axis, an output circuit' con nected to said anodes in push-pull relation, a delecting system arranged to deilect said beam in the plane of said anodes, a source o! alternating current o! fixed frequency. means for energizing said deflection system from said source to alternately deiiect the beam from one anode to anothervat the frequency of said sourceand at a constant amplitude, a second deiiecticn system arranged to deflect said beam in the plane ot said anodes, and a source of signal current for' energirlng said second defiecting system to shift the mean position of'said'beam to one side or the other of said axis in the plane oi' said anodes, and said anodes having a dimension in the direction. of deflection of said beam relatively large with respect to the transverse dimension of said beam in the same direction.

2. A combination according lto claim iwherein said anodes are elongated in their common plane and serve to intercept said beam at all angles of' deection. j

3. In combination, an electron tube including vmeans for establishing an electron Vbea-xn along ja givenaxis, a pair of anodes arranged on oppo- .site sides of said axis, an output circuit connected to said anodes in push-pull` relation, means for alternately deecting said beam from. one anode to the other at nxed frequency and constant amplitude, and signal control means for shifting the mean position of said beam in the plane of said anodes, said anodes having a dimensionin the direction of deflection/of said beam relatively large withrespect to the transverse dimension ot said beam in the same direction.

PAUL GLASS.

,QREFERENCES CITED The following references are of record in the Nagy et a1 Mar. 1s, 1943 

